JPH0952007A - Acid resistant filter - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide excellent properties such as heat resistance, chemical resistance and durability as a filter cloth without impairing the properties of the meta-type aromatic aramid fiber even in a severe acid atmosphere. To provide an acid resistant filter having. SOLUTION: The felt is integrally formed on a base cloth in which the warp is a meta-aramid fiber and the weft is a polytetrafluoroethylene fiber, and the felt is treated with inorganic fine particles and a fluorine-based resin. .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acid resistant filter. More specifically, the present invention relates to an acid resistant filter used as a bag filter or the like for collecting fine particles in exhaust gas from an urban refuse incinerator, factory exhaust gas, and the like.

[0002]

2. Description of the Related Art At present, various filters are known as dust collecting filters. The fibers generally used as the dust collecting filter fibers are metal fibers, glass fibers, aramid fibers, and the like, and meta-aramid fibers are particularly often used. Meta-type aramid fiber has excellent heat resistance, and it is widely used in fields exposed to high temperatures as a material for bag filters that collects fine particles in exhaust gas from, for example, municipal waste incinerators. . However, since the exhaust gas contains sulfuric acid mist, hydrochloric acid mist, etc. and is operated at a high temperature for a long time, there is a problem that the filter cloth deteriorates and the bag is easily damaged during the process. is there. For this reason,
As a heat and chemical resistant filter, various methods have been proposed for improving the heat resistance, chemical resistance, durability, etc. of the filter by adhering a fluororesin, a silicone resin, colloidal alumina or the like to a heat resistant base cloth. For example, "when the inorganic fiber cloth such as glass fiber is treated with silicon, polytetrafluoroethylene resin, graphite or the like for a filter, it is treated with colloidal alumina in advance, or silicon or polytetrafluoroethylene is used. By performing treatment with colloidal alumina at the same time as treating resin, graphite, etc., 0.03 to 5
A method for treating a filter cloth for high temperature in which alumina is adhered in the range of wt%. (Japanese Examined Patent Publication No. 47-14866), "Improved wholly aromatic polyamide fiber and cloth, which are obtained by treating wholly aromatic polyamide fiber and cloth with a fluorine resin emulsion and applying the fluorine resin coating. (Japanese Patent Application Laid-Open No. 56-107073), "The fiber surface of the fiber structure made of aromatic polyamide fiber is
A chemical resistant filter material, which is coated with one or more compounds selected from the group consisting of oxides of silicon, aluminum, lithium and the like and a fluororesin. (JP-A-61-1492)
No. 17, for example) is disclosed. However, even with these technologies, heat resistance, chemical resistance, durability, etc. are not perfect.

[0003]

SUMMARY OF THE INVENTION The present invention has been made under the circumstances described above, and an object thereof is to maintain the characteristics of the meta-type aromatic aramid fiber even in a harsh acid atmosphere. Another object of the present invention is to provide an acid resistant filter having excellent heat resistance, chemical resistance and durability as a filter cloth.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
An acid-resistant filter obtained by integrally molding a felt on a base fabric having a warp as a meta type aramid fiber and a weft as a polytetrafluoroethylene fiber, wherein the integrally molded felt is made of inorganic fine particles and a fluorine-based material. It is achieved by an acid resistant filter treated with a resin.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Carbon fibers, metal fibers, glass fibers, organic heat resistant fibers, etc. are conventionally known as fibers constituting a base cloth or felt used for heat resistant filters. Known heat-resistant fibers include meta-aramid fibers, polyphenylenetriazole fibers, polyoxythiazole fibers, polyimide fibers, and polybenzimidazole fibers. In the present invention,
As the base fabric for integrally molding the felt, a woven fabric using meta-aramid fiber as the warp and polytetrafluoroethylene fiber as the weft is used, and is usually used in the form of a scrim. Here, the meta-type aramid fiber is a fiber formed of a polymer or a copolymer thereof produced by the reaction of a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid, and among them, by a reaction of metaphenylenediamine and isophthalic acid chloride. Fibers based on the resulting polymetaphenylene isophthalamide are preferred.
In addition, since the bag filter usually receives tensile stress in the direction of the weft due to the pulse when the collected dust is removed by the bag filter, it is important to use fibers with high elongation as well as chemical resistance. Polyethylene fiber (PTFE fiber) is preferable.

As the fibers constituting the felt, any of the above-mentioned conventionally known fibers can be used, but meta type polyamide fibers, particularly fibers containing polymetaphenylene isophthalamide as a main component are preferable.

Alumina, silica, zirconium, and the like, and hydrates thereof can be used as the inorganic fine particles used for treating the felt integrally molded with the base cloth, that is, for the acid-resistant processing of the filter, and especially alumina sol. Is preferred. Although inorganic fine particles other than alumina sol are also effective, they may cause handling problems such as an increase in hardness of the work cloth after the treatment. The alumina sol referred to here is a colloidal alumina hydrate having an average particle size of 5 to 200 mμ, which is usually a suspension in which anions are dispersed in water as a stabilizer, and the alumina itself is Since it is positively charged, anions are coordinated on the surface of the alumina particles and in the vicinity thereof, which gives stability to the colloid. Note that the particle shape is not particularly limited, and a spherical shape or a feather shape can be used. However, since the feather shape has a lot of entanglement with the fiber, the particle shape is different from the spherical shape. It is preferable because a filter having excellent durability can be obtained. One of the feather-like particles is formed by polymerizing about 600,000 alumina particles, and has particularly good heat resistance and chemical resistance.

The amount of the inorganic fine particles adhered is 10 to 25% by weight based on the weight of the felt fiber. If it is less than 10% by weight, it may be difficult to make uniform adhesion, and variations in acid resistance may occur. On the other hand, if it exceeds 25% by weight, the felt may be deposited between the fibers constituting the felt, resulting in insufficient air permeability as the felt.

Next, the fluororesin used for the treatment of felt is, for example, polytetrafluoroethylene (abbreviation: PTF).
E), tetrafluoroethylene / perfluorovinyl ether copolymer (abbreviation: PFA), tetrafluoroethylene / hexafluoropropylene copolymer, and the like. These fluorine-based vinyl polymers are usually used as a dispersion (dispersion liquid) dispersed in water in the form of fine particles. In addition, in order to improve the sticking property to the felt, it is preferable to add and blend a fluorinated urethane compound represented by the following formula (Formula 1) as a binder component.

[0010]

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In the formula, R represents an alkyl group, preferably an alkyl group having 1 to 5 carbon atoms, and Rf represents a perfluoroalkyl group, preferably a perfluoroalkyl group having 1 to 5 carbon atoms. Moreover, n is an integer of 1-8.

Examples of such a fluorinated urethane compound include an aliphatic isocyanate compound such as hexamethylene disocyanate, an active hydrogen compound containing a perfluoroalkyl group such as β-perfluoroalkylethyl alcohol, and an aliphatic alcohol. The urethane compound which makes a reaction product a main component can be illustrated. The mixing ratio of the fluorinated vinyl polymer and the fluorinated urethane compound is preferably about 1: 1 in terms of solid content, which shows the best performance. If this balance is lost, the hardness of the processed resin coating will become too hard, or the adhesion to the felt will decrease.

The amount of the fluororesin deposited (the total amount of the fluorovinyl polymer and the fluorinated urethane compound) is 5 to 12% by weight based on the weight of the fiber. If the amount is less than 5% by weight, it becomes difficult to uniformly attach the fluorine-based resin, and the portion where the fluorine-based resin is less attached tends to be deteriorated, and sufficient acid resistance cannot be obtained. On the other hand, when it exceeds 12% by weight, the felt hardness becomes too high, and troubles are likely to occur during bag sewing.

In order to manufacture the acid-resistant filter of the present invention described above, for example, the warp is made of meta-aramid fiber,
First, a felt is prepared by arranging cut cotton of meta-type aromatic aramid fiber on a base cloth using polytetrafluoroethylene fiber as a weft yarn and performing needle punching to integrate with the base cloth. Next, this felt is processed, but in the present invention, the treating agent containing the inorganic fine particles and the treating agent containing the fluororesin may be treated separately, or treated with the treating agent containing both of them. You may. However, when they are treated separately, they are first treated with a treatment agent containing inorganic fine particles and then treated with a treatment agent containing a fluororesin. By doing so, the acid resistance of the resulting filter and its durability are further improved, which is more preferable. For example, first, it is impregnated with feather-like alumina sol (concentration about 10%) and dried at 105 to 150 ° C.
Heat treatment is performed at ˜210 ° C., subsequently, it is impregnated with a fluorine-based resin (concentration: 10 to 20%) in which a fluorinated urethane compound is added to the PTFE fine particle aqueous dispersion, and squeezed with mangle to dry at 105 to 150 ° C. Then 190-210
By performing the heat treatment at ℃, it is possible to obtain an acid resistant filter having an appropriate hardness and a resin adhesion amount.

[0015]

The present invention will be described below in detail with reference to examples. The performance evaluation in the examples was carried out by the following method. <Acid resistance retention> The filter sample was immersed in a 7% aqueous solution of sulfuric acid and kept in a reduced pressure atmosphere of 80 mmHg for 3 hours to uniformly permeate sulfuric acid into the felt of the filter sample. Then, the sample was taken out, the sulfuric acid adhering to the surface was lightly wiped off, and the sample was kept as it was for 1 hour in a hot air dryer set at 200 ° C. The acid resistance performance was evaluated from the strength change (strength retention rate) of the felt before and after this treatment. <Felt Hardness> The sample was cut into a width of 10 mm, placed on a support having a span of 5 cm, and the hardness was evaluated by measuring the amount of deflection when a load of 10 g was placed in the center. .

[Examples 1 to 5 and Comparative Examples 1 to 3] The warp was made of meta-aramid fiber (trade name: Conex, manufactured by Teijin Limited), and the weft was made of polytetrafluoroethylene (PTF).
E) A scrim made of fibers (a plain weave mesh fabric made of 1000 denier fibers in both length and width: 13 to 15 yarns / inch for both warp density and weft density) was used.
With this scrim as the base fabric, the single yarn fineness is 2 on both sides.
Denier and 51 mm long meta-type aramid short fibers (trade name: Conex, manufactured by Teijin Ltd.) are placed at a weight of 500 g / m ^2, and needle punching is applied to this to be integrated with the base fabric. I made a felt.

The felt obtained was dipped in an aqueous dispersion of feather-like alumina sol (trade name: AS-200, manufactured by Nissan Chemical Co., Ltd., concentration 10%), squeezed, and dried at 150 ° C. A heat treatment was performed at 200 ° C. to deposit feathered alumina in the amount shown in Table 1 with respect to the fiber weight. Then
85 parts by weight of PTFE aqueous dispersion (trade name: AD-1, manufactured by Asahi Glass Co., Ltd., concentration 60%) and fluorinated urethane compound (trade name: AG3001, manufactured by Asahi Glass Co., Ltd., concentration 20)
%) 255 parts by weight of water and 415 parts by weight of water were dipped in a treatment solution, squeezed and dried at 150 ° C.
Heat treatment was carried out at 0 ° C., and the fluororesin was attached at a ratio shown in Table 1 with respect to the fiber weight. The results are shown below.

[0018]

[Table 1]

[0019]

The acid-resistant filter of the present invention exhibits excellent heat resistance, chemical resistance, durability, etc. even in a more severe high-temperature acidic atmosphere. It can be suitably used for a bag filter or the like for collecting fine particles in exhaust gas.

Claims (4)

[Claims] 1. A filter in which felt is integrally molded on a base fabric, wherein the warp of the base fabric is meta-aramid fiber,
An acid-resistant filter characterized in that the weft is a polytetrafluoroethylene fiber, and the felt integrally molded with the base cloth is treated with inorganic fine particles and a fluororesin. 2. The acid resistant filter according to claim 1, wherein the inorganic fine particles are alumina. 3. The acid resistant filter according to claim 2, wherein the alumina is feathery alumina. 4. The acid resistant filter according to claim 1, wherein the felt is made of meta-aramid fiber.